Add RequestFactory validator implemented as an annotation processor.
This will eventually replace the RequestFactoryInterfaceValidator and it's
classfile-based approach.
Patch by: bobv
Review by: t.broyer, pquitslund

Review at http://gwt-code-reviews.appspot.com/1467804


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10417 8db76d5a-ed1c-0410-87a9-c151d255dfc7